Milling machine



Dec. 26, 1939.

J. T. BOLAS MILLING MACHINE Filed March 24, 1959 3 Sheets-Sheet l Dec. 26, 1939. J. 'r. BOLAS MILLING MACHINE Filed March 24, 1939 3 Sheets-Sheet 2 Dec. 26, 1939. J. T. BOLAS MILLING MACHINE Filed March 24, 1939 3 sheets sheet 5 fvwenfr Patented Dec. 26, 1939 UNITED STATES PATENT OFFICE MILLING MACHINE Application March 24, 1939, Serial No. 263,977 In Great Britain May 2a, 1939 1 Claim. (Cl. 90-185) This invention relates to milling and like machines, for copying and reproducing, of the kind in which a feeler co-operates with a former or pattern to control the movement of the cutter 5 with respect to the work. The object of the invention is to provide a machine of this kind in which the relative traversing movement between the cutter and the work is automatically and rapidly reversed at the end of each traversing inovement of the feeler with respect to the pat- According to the invention, a machine of the kind described comprises a reciprocating hydraulic motor for traversing a feeler with respect to a pattern and a cutter with respect to the work, valve-mechanism associated with said motor for automatically reversing it, electrical means controlled by pressure between the feeler and the pattern and an interconnection between 20 the electrical means and said valve. The said interconnection is preferably a quick-acting relay. For example, the said valve may be operated pneumatically, the pressure-gas being controlled by said electrical means.

25 A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings which illustrate a machine designed for the purpose of cutting the inter-fln spaces in the cylinder-heads or 30 cylinder barrels of an air-cooled internal-combustion engine. In the drawings:

Figure 1 is a plan, Figure 2 a front elevation, and Figure 3 a side elevation of the complete machineshowing its general arrangement, and

35 Figure 4 is a diagram showing the electrical,

pneumatic and hydraulic circuits.

As shown in Figures 1, 2 and 3, the machine comprises a bed-plate I and supporting frame II which carry a work-table l2 carried on an 40 adjustable slide l3. The frame II also carries a cutter-head l4 comprising a milling cutter l5 driven by an electric motor IS. The cutter-head is carried on a table-l1 which is slidable from left to right, as seen in Figures 1 and 2, on a 45 slide l8. The table I! is fixed to the end of a piston rod [9 of which the piston 20 reciprocates in a hydraulic cylinder 2| carried by a fixed part 22 of the machine frame. The table I! also carries a downwardly-projecting pin 23 50 which constitutes a feeler and co-operates with a former or pattern comprising a plate 24 car ried by the work-table l2.

The pattern 24 is cut with a notch 25 of which the profile is a prototype of the shape which is 55 to be cut in the work 26.

In order that the functions of the various parts described with reference to Figure 4 may be clearly understood the operation of the machine will first be described. The hydraulic motor 2| reciprocates the table H from left to right as 5 shown in Figure 1. When the feeler 23 abuts against the edge of the slot 25 in the pattern 24 a series of automatic operations ensues whereby the direction of movement of the piston is reversed and at the same time a gear 21 is 10 rotated through a small angle; the gear 21 is carried on the end of a feed-screw (not shown) which advances the work-table through a short distance towards the milling cutter l5. At the end of the next traversing stroke of the feeler 23 with respect to the notch the piston 20 is similarly reversed and the feed-screw similarly rotated, so that a slot 28 is cut in the work 25 to a shape corresponding to the shape of the notch 25 in the pattern 24. 20

In this specific embodiment the diameter of the cutter is equal to the vertical dimension of the slot to be cut in the work, so that only two relative movements need to be provided for; (1)

a traversing movement of the cutter-head I4 25 from left to right, as seen in Figures 1 and 2, and (2) a depth-feed by which the work is fed towards the cutter whereby the cutter penetrates the work. However, where the invention is to be applied to the cutting of shapes of which no dimension is equal to the size of the cutter a third component of relative movement between the cutter and the work would need to be pro.- vided, either automatically or otherwise.

In the diagram of Figure 4 the feeler 23 is shown as a rod pivoted at 29 to the table I! and projecting downwardly into the notch 25 in the pattern 24. The rod. 23 carries between its ends a collar 30 carrying electric contacts 3|, 32 which co-operate respectively with fixed contacts 33, 34, the contact portions 35, 36 being pressed towards a limiting innermost position by means of suitable springs 31, 38. The rod 23 also carries a collar 39 which is acted upon by two compression springs 40 and 4| which tend to maintain the rod 30 in a central position as shown. The rod 23 is assumed to be connected to earth so that only one conductor of each electric circuit need be described. The electric contact 33 is connected by a conductor 42 to a solenoid 43, the other end of the winding of which is connected by a conductor 44 to a battery 45, or other source of electric current, the other pole of which is earthed as shown at 46. The other electric contact 34 is connected by a conductor 4'! to a cutter.

' The solenoid 43 controls an armature 59 carrying a pin at its lower end, the pin engaging alever 52 which is pivoted at one end to an anchorage 53 and which is formed at its other end with a fork 54 lying between collars 55 on the tube or stem 58 of a pneumatic valve. The solenoid 48 similarly controls a yoke 58 which operates in a like manner .upon the stem 59 of another pneumatic valve. 7

The stems 58 and 59 are formed respectively with conical valve members 89, 8| which control conduits 82, 83, communicating with a valve chest 54, to which compressed air is admitted through a pipe 85. The conduit 82 leads to the end of an air-cylinder 88 containing a piston 81 having a piston-rod 88. The conduit 83 similarly leads to an air-cylinder 89 in which a piston 19 is slidable. The piston-rods 88 and 1| are respectively guided in glands 12, 13, and abut against either end of a hydraulic .valve which will now be described.

The cylinder 14 of the valve is supplied with oil under pressure through a pipe in a manner described below. Two delivery pipes 18,11 lead respectively to the left-hand and right-hand ends of the hydraulic cylinder 2|, the piston 29 of which performs the traversing movement of the g The cylinder is also formed with two drain ports which lead by pipes 18, 19, to a drain 89.

The valve member comprises a middle land 8| and end lands 82, 93, the three lands being separated by rod portions 84. 85, of reduced diameter. It will be seen that, when the valve is in the position shown, oil under pressure can flow from the pipe 15 around the portion 84, and

through the pipe 18 to the left-hand end of the cylinder 2|, and that oil discharged from the right-hand end of'the piston 29 can flow by way 01' the pipe 11 around the rod 95 to the drain 89. When the valve is moved to the left the land 8| moves to the left of the pressure port, so that the pipe 15 supplies oil under pressure to the pipe 11 and oil is drained from the pipe 18 around the rod 84 into the pipe 18.

The oil pressure is generated by means of a pump 85 of the gear-wheel type which may be driven by an electric motor indicated at 88 in Figure 1. Oil is taken in from a suitable sump through a pipe 81 and delivered to the interior of a control-valve 88 through the pipe 89. The valve member 99, when in the position shown in Figure 4, permits the oil from the pipe 89 to pass into the pipe 15, but when a hand-lever 9| is rocked in a counterclockwise direction the valve 99 closes the admission to the pipe 15 and connects the pipe 89 to a drain 92 which leads back to the sump.

The depth-feed is efl'eoted by -a hydraulic motor 93 of the rotary type which is supplied with oil under pressure through a branch 94 from the pipe 15 and which discharges oil through a pipe 98 leading back to the sump. The motor is controlled by an escapement of known type comprising a pallet-wheel 95 and a pallet .91 pivoted at 98. The pallet carries teeth 99, I99, and the wheel 95 carries teeth I9I, I92, etc. The motor 93 tends to rotate in the direction of the arrow, but is normally restrained against movement by the abutment of the tooth |9| against the tooth I99. When the pallet 91 is rocked in a counterclockwise direction the tooth I90 moves 0 1; OI

engagement with the tooth I9I whereby the wheel 95 is temporarily released and the tooth I9| moves downwardly. However, the tooth I92 strikes against the inclined surface of the tooth 99, whereby the pallet is rocked back to its original position and the wheel 95 is brought to rest with the tooth I92 abutting againstthe tooth I99. Similarly, whenever the pallet 91 is rocked about its pivot the wheel 95 advances through'one' tooth.

The escapement is controlled by an air-relay I93 comprising an outer cylinder and a fixed partition I94. Above the partition is a piston member I95 having a rod I98 to engage the pallet 91 partition and abuts against the underside oi the piston I95. The cylinderspace above the partition is connected by a pipe I99 with the air-pipe 88, and the space below the piston 91 is connected by a pipe I I9 with the air-pipe 82.

The operation of the apparatus diagrammatically shown in Figure 4 will now be described. Assuming that the piston 29 is being driven to the right by oil under pressure from .the pipes 15, 18, the bottom of the feeler 23 will eventually abut against the right-hand edge of the notch 25. The movement of the feeler'23 will thereupon be arrested, although movement-of the table I1 to the right will tend to continue. Consequently, the feeler 23 will rotate through a small angle about the pivot 29 whereby the electric contact 3| will engage the contact member 35 and the solenoid 43 will be energised. The armature 59 will raise the lever 52 whereby the valve member 89 will open the pipe 82 and air under pressure from the pipe 85 will be admitted to the righthand end .of the cylinder 88. Consequently, the piston 81 will move to the left and the rod 88 will slide the hydraulic valve 8|, 82, 83, towards its extreme left-hand position. The consequent movement of the piston 19 to the left discharges air from the cylinder 99 along the pipe 83, through the interior of the valve-stem 59. Movement of the hydraulic valve to the left reverses the pressure and drain circuits in the manner already explained, so that oil under pressure is now admitted through the pipe 11 to the righthand and of the cylinder 2|, and the oil from the left-hand end of the cylinder 2| is drained away through the pipe 18. Consequently, the movement of the piston 29 is immediately reversed and the table I1 begins its traverse towards the left. Air isprevented from escaping from the chest 84 through the stem 59 by the closed end of the tube I59 which seals the interior of the stem. In Figure 4 the stem 58 is shown in the position in which it is closed by the tube I58 the top of which opens into a tube I59 of larger in-- ternal diameter than'the stem so that the air can escape as shown by the arrows.

The opening of the valve member 89 also admits air from the pipe 85 to the pipe 9 whereby the piston I91 rises, causing the rod I 98 to lift the piston I 95, whereby the rod I 98 actuates the escapement so as to cause the wheel. 95 to rotate in the manner already described. The space between the piston I 91 and the partition I94 .is maintained at atmospheric pressure by a vent I39. The shaft I II of the escapement wheel carries a gear 2 which drives a gear II3 engaging the gear 21 (see Figures 2 and 3), whereby the feed-screw is rotated through the necessary angle. On the'same shaft as the gear I I3 a suitable hand-wheel H4 is mounted for manually adjusting the ifeed.

At the end of the traverse of the table I! towards the left, that is to say, when the feeler 23 strikes the left-hand end of the notch 25 in the pattern 24, the contact 3i! closes the circuit 41 of the solenoid 48, whereby the valve 6| opens the air-pipe 63 and the piston Ill drives the hydraulic valve 8|, 82, 83 towards the right into the position shown. Thus, the movement of the traversing piston 20 is again reversed and the machine continues automatically in this fashion until the slot 28 in the work has been cut to the required depth. When the valve 6| opens air is admitted through the pipe I09 to the space between the partition I04 and the piston I 05, whereby the escapement is actuated and the depth-feed advanced. Thus, the depth-feed is advanced every time the table I! reaches the end of its traversing movement.

The rate at which the table I! is traversedtable II. The valve 60 is shown open for the pur-.

poses of illustration. Also, ports H9 and I20 are formed in the air-cylinders 66, 69, respectively to relieve air from the opposing faces of the pistons 61, I0. For a like reason drain conduits l2l, I22 are provided at the ends of the valve cylinder 14; v

Automatic mechanism (not shown) may also be provided whereby themachine is automatically stopped when the depth-feed has proceeded to a predetermined extent.

It will be seen that by the provision of an electriccircuit controlled'by the feeler, a very sensitive action of the feeler is possible. The valve .64, the cylinders 66, 69 and the pistons 61, I0 constitute a pneumatic relay controlled by the electric circuit so that the current supplied to the electric circuit may be kept low and yet sufllcient power is obtainable for shifting the hydraulic piston-valve. A pneumatic relay has the advantagethat it is quick-acting. A hydraulic motor for reciprocating the slide has the advantage that it is steady and powerful.

It will be understood that the relative move be held stationary and the traversing movementefiected by reciprocation of the work and the 1 pattem-plate.

I claim: v

A millingmachine comprising a cutter to cooperate with the work and a feeler to co-operate with a pattern, a reciprocating hydraulic motor for traversing the feeler with respect to-the pattern and the cutter with respect to the work, valve mechanism associated with said motor for automatically reversing it, electrical controlmeans actuated by pressure between the feeler and pattern, an interconnection between said electricalcontrol-means and the said valve, a. rotary hydraulic motor to drive an intermittent depth-feed, an escapement normally operative to lock the motor against rotation and a pneumatic relay actuated by said electrical means to release the escapement whenever the feeler abuts against the pattern.

JOHN THOMAS BOLAS. 

